This invention relates to the field of mining in general, and to coal-mining in particular.
More specifically, the invention relates to a method of and to an apparatus for mining of coal and of other minerals which are mined in a similar manner as coal.
The tightening situation with respect to the availability of crude oil for fuel and petrochemical uses, is increasingly focussing attention on coal as an alternative. And indeed, the use of coal as a substitute for oil holds great promise. The major bottleneck in the development of unprecedented numbers of applications for coal resides not in technology for the conversion of coal into liquid fuels and petrochemicals; it resides in the technology of extraction.
Extraction speed is comparatively low when considering the huge demand that will be facing the industry in the near future.
Percentage of recovery is also relatively low, on the order of only about 65-75%, which means that between about 25-35% of all mineable coal has heretofore been written off as non-extractable and thus lost forever. This represents a loss of natural resources which is not only intolerable in view of the energy problems confronting the United States, but is also avoidable as e.g., the West German experience has shown, where extraction--albeit under different conditions--amounts to about 95% of the available coal.
A further deterrent to high-volume coal use heretofore has been the rather high extraction cost. Although in the face of steadily rising oil prices the question of extraction economy is no longer as pressing as before, it is still desirable to be able to reduce extraction costs.
And finally, but certainly not lastly, there has been heretofore always been a very significant physical and health hazard inherent in being a coal miner. Conditions below ground do not contribute to making the mining of coal one of the more sought-after occupations. An interesting fact is that the majority of underground mining accidents happen in the process of providing support for the roof within 30 feet of the solid mine face, a problem which will be overcome by the present invention.
All of this will have to be changed if the mining industry is to be able to live up to the national hopes placed in it as a replacement for the suppliers of oil.